Igniter for an internal combustion engine

ABSTRACT

An igniter for an internal combustion engine using a semiconductor switch is disclosed. A voltage dropping element is selectively inserted in a feeding circuit of an ignition coil of the engine which is connected to a DC electric source during the time of initiation of the engine or during a normal operation so as to compensate for a battery voltage drop at the time of initiation of the engine. A diode is provided for feeding a base current directly to the semiconductor switch at the time of ignition of the engine by short-circuiting the voltage dropping element at such time. A decrease in the base current of the semiconductor switch at the time of initiation of the engine, due to the voltage dropping element, is thereby avoided. The semiconductor switch is thus sufficiently conducted at the time of initiation of the engine, such that sufficient current is fed to the ignition coil so as to improve the ignition efficiency at the time of initiation of the engine.

United States Patent [191 Miki et a1.

[ IGNITER FOR AN INTERNAL COMBUSTION ENGINE [75] Inventors: Takao Miki,l-limeji; Toshikazu Saita, Takasago, both of Japan [73] Assignee:Mitsubishi Denki Kabushiki Kaisha,

Tokyo, Japan 22 Filed: Feb. 22, 1972 21 Appl. No.: 227,857

[30] Foreign Application Priority Data Feb. 23, 1971 Japan 46-10838 [52]US. Cl. 123/179 BG, 123/148 E [51] Int. Cl. F02p 3/02 [58] Field ofSearch 123/148 B179 86; 315/209 T; 290/37, 38

[56] References Cited UNITED STATES PATENTS 3,173,410 3/1965 McLaughlin123/179 BG 3,180,997 4/1965 Short et a1. 290/38 3,434,463 3/1969 Bartch123/148 E [451' July 2, 1974 Primary Examiner-Laurence M. GoodridgeAttorney, Agent, or FirmOblon, Fisher, Spivak, Mc- Clelland & Maier [57]ABSTRACT An igniter for an internal combustion engine using asemiconductor switch is disclosed. A voltage dropping element isselectively inserted in a feeding circuit of an ignition coil of theengine which is connected to a DC electric source during the time ofinitiation of the engine or during a normal operation so as tocompensate for a battery voltage drop at the time of initiation of theengine. A diode is provided for feeding a base current directly to thesemiconductor switch at the time of ignition of the engine byshort-circuiting the voltage dropping element at such time. A decreasein the base current of the semiconductor switch at the time ofinitiation of the engine, due to the voltage I dropping element, isthereby avoided. The semiconductor switch is thus sufficiently conductedat the time of initiation of the engine, such that sufficient current isfed to the ignition coil so as to improve the ignition efficiency at thetime of initiation of the engine.

2 Claims, 4 Drawing Figures PATENTEDJUL 2 i974 FIG.

FIG.2

FIG.3

BACKGROUND OF THE INVENTION ,cludes a semiconductor such as a transistoror thyristor having a base circuit 10. An interrupter 11, an excitingcoil 12 of an electric source generator for supplying an electriccharge, and a starter 13 are also provided.

The operation of the igniter for an internal combustion engine as shownin FIGS. 1 and 2 will now be described. ln FIGS. 1 and 2 it should beunderstood that the interrupter II is shut and opened to thereby shutand open the semiconductor switch 9 and accordingly interrupt theelectric current of the ignition coil 8. When initiation of the engineis desired, the moving element of the keyswitch 1 is connected to thecontacts 3 and 4 as is shown in FIG. 2 and accordingly, the starter I3is actuated. At such time, an electric current is fed through thecontact 3 to the ignition coil 8, and to the base circuit through theresistor 7. Electric current is also fed through the resistor 7 to theexciting coil 12. Since the voltage drop across the resistor 7 is high,the electric current in the base circuit 10 is extremely low. As aresult of the low current in the base circuit 10, the semiconductors,such as the transistors in the switching circuit 9, cannot completelychange to a closed condition. The electric current of the ignition coil8 will also be of an extremely low value. Because of the above, itbecomes impossible to initiate the engine, and the same, thereby, isinoperable.

In the past, in an unsatisfactory attempt to overcome the above problem,the base circuit 10 would be connected between the resistor 7 and theconnecting point of the ignition coil 8. Additionally, the value of theresistors connected to the base circuit 10 would be decreased, so as toprevent a low base current caused by the voltage drop in the resistor 7.One problem with decreasing the value of the resistors connected to thebase circuit 10 is that the same can be easily burned and thereby,rendered inoperative.

Others have attempted to eliminate the outer resistor 7 entirely, butunder such conditions, the inner resistance of the ignition coil 8 isgreatly increased.

A problem with increasing the inner resistance of the ignition coil 8 isthat an overcurrent will be fed to the base circuit 10 during theoperation of the engine, whereby again, the resistors of the basecircuit 10 can be burned and ultimately rendered inoperative.

SUMMARY OF THE INVENTION It is an object of this invention to' provide anew and improved unique igniter for an internal combustion enginewherein the igniter uses a semiconductor switch which has a base circuitthat can be fed a sufficient current at the time of initiation of theengine.

Briefly, in accordance with thepresent invention, the foregoing andother objects are in one aspect attained by the provision of an igniterfor an internal combustion engine which includes a first feeding circuitfor feeding electric current through an outer resistor to an ignitioncoil and a second feeding circuit for feeding electric current from theelectric source to the ignition coil without passing through the outerresistor. A semiconductor switch is provided for switching the electriccurrent of the ignition coql and the same includes a base circuit. Amoving element is provided for at least connecting the base circuit ofthe semiconductor switch to the electric source during a normaloperation of the engine. Finally, a diode is provided and is connectedbetween the base circuit and a terminal of the ignition coil for feedingthe electric current of the second feeding circuit to the base circuitwithout passing, at the time of initiation of the engine, through theouter resistor.

BRIEF DESCRIPTION OF THE DRAWINGS A more complete appreciation of theinvention will readily be obtained as the same becomes better understoodby the accompanying drawings wherein:

FIG. 1 is an electrical schematic diagram showing the operation of aconventional igniter, using a semiconductor switch, during normaloperation;

FIG. 2 is an electrical schematic diagram showing the operation of theconvention igniter of FIG. 1 during initiation of an engwne;

FIG. 3 is an electrical schematic diagram of one preferred embodiment ofthe igniter of the present invention; and,

FIG. 4 is an electrical schematic diagram of another preferredembodiment of the igniter of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS base circuit 10 and theconnecting point A of the resstor 7 and the ignition coil 8.

When initiation of the engine is desired, electric current is fed fromthe connecting point A through the diode 14 to the base circuit 10.Accordingly, sufficient base current is fed so as to place thesemiconductor switch 9 in a completely closed condition. A large amountof electric current will also be fed to the ignition coil 8 and as such,the engine can be easily initiated.

With the present arrangement, since the base circuit 10'is directlyconnected to the contact 2, it is unnecessary to decrease the resistancein the circuit. Accordingly, there is no possibility of an accidentwhich could cause burning of the resistors in the base circuit 10. Inthe embodiment of FIG. 3, it is apparent that the base current isincreased by the use of the diode 14. However, since the electriccurrent of the exciting coil 12 is also fed to the diode 14, a diodehaving a large current capacity is required.

FIG. 4 shows an alternative preferred embodiment of the igniter of thisinvention wherein another diode 15 is inserted. With the use of a seconddiode, the electric current rating of the diode 14 can be decreased,whereby the igniter can be even more compact and of a lower cost.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within operation of said engine;

a semiconductor switch for switching the electric current throughsaidprimary winding, said semiconductor switch including a base circuitconnected directly to said power source during the normal operation ofsaid engine;-

diode means connected between said base circuit and said terminal ofsaid primary winding for increasing the conduction of said semiconductorswitch during the cranking operation of said engine thereby increasingthe voltage at said terminal of said primary winding whereby the currentfrom said power source through said primary winding is increased duringsaid cranking operation of said engine.

2. The igniter for an internal combustwon engine according to claim 1,further comprising a second diode connected directly between said basecircuit and said power source during the normal operation of saidengine, said second diode connected in parallel with said first diodemeans and biased so as to feed electric current to said base circuit.

1. An igniter for an internal combustion engine, which comprises: anelectric power source; an ignition coil having a primary winding; aresistor connected between said power source and said primary winding ofsaid ignition coil during the normal operation of said engine; meansconnecting said power source directly to a terminal of said primarywinding during the cranking operation of said engine; a semiconductorswitch for switching the electric current through said primary winding,said semiconductor switch including a base circuit connected directly tosaid power source during the normal operation of said engine; diodemeans connected between said base circuit and said terminal of saidprimary winding for increasing the conduction of said semiconductorswitch during the cranking operation of said engine thereby increasingthe voltage at said terminal of said primary winding whereby the currentfrom said power source through said primary winding is increased duringsaid cranking operation of said engine.
 2. The igniter for an internalcombustwon engine according to claim 1, further comprising a seconddiode connected directly between said base circuit and said power sourceduring the normal operation of said engine, said second diode connectedin parallel with said first diode means and biased so as to feedelectric current to said base circuit.